Hydraulic pump structure



July 2, 1957 F. A. SHERMAN 2,797,643

HYDRAULIC PUMP STRUCTURE Find Dec. 7. 1953 s sheets-sheet 1 OUTLETUNH-ET INVENToR.

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HYDRAULIC PUMP STRUCTURE Filed D60. '7, 1953 3 Sheets-Sheet I5 To DRAINFmi IN VEN TOR.

wm www ATTORNEYS HYDRAULIC PUMP STRUCTURE Flo d A. Sherman Birmingham,Mich., assigner to Motor Pxioducts Corpoiation, Detroit, Mich., acorporation of New York Application December 7, 1953, Serial No. 396,6701 Claim. (Cl. 103--38) This invention relates generally to pumpsandrefers more particularly to improvements in rotary displacement pumps. a

It is an object of this invention to providea compact pump structurehaving a high output capacity in comparison to its size and capable ofsupplying fluid at relatively high pressures.

It is another object of this invention to provide a pump structurecomposed of a relatively few simple parts capable of being inexpensivelymanufactured and installed.

It is still another object of this invention to provice means operatedby the pressure of the fluid at the discharge side of the pump forvarying the output of the pump and rendering it possible to displace asubstantially uniform quantity of iluid at practically constant lluidpressure regardless of variations in the speed of the pump.

The foregoing as Well as other objects will be made more apparent asthis description proceeds especially when considered in connection withthe accompanying drawings, wherein:

Figure 1 is a side elevational view of a pump embodying the features ofthis invention; n

Figure 2 is a sectional View taken on the line 2-2 of Figure 1; n

Figure 3 is a cross sectional View taken on the line 3-3 of Figure 2; s

Figure 4 is a sectional view similar to Figure 3 looking in the oppositedirection; n

Figure 5 is a cross sectional view taken on the line 5-5 of Figure 2;

Figure 6 is a semi-diagrammatic sectional vlew of a modified pumpstructure; and I Figure 7 is a sectional view similar to Figure 6showing the control valve in a different position.

Referring now more in detail to the drawings, it will be noted that thenumeral 10 designates a rotary pump of the displacement type having acasing 11 comprising two parts 12 and 13. The part 12 has a rear wall 14and has an annular Wall 15 projecting forwardly from the rear wall 14.The rear wall 14 is fashioned with diametrically opposed inlet andoutlet ports 16 and 17 respectively. The front surface of the rear wall14 is fashioned with an arcuate recess 18 which, in the presentinstance, extends for approximately 180 and communicates with the inletport 16. The front surface of the rear wall 14 adjacent the recess 18 isformed with an arcuate slot 2t) concentrically arranged with respect tothe recess 18 and positioned diametrically opposite the latter. The slot20 extends for approximately 90 and coinmunicates with the outlet port17.

The part 13 of the casing 10 is generally cup-shaped and has a radiallyoutwardly extending annular flange 21 at the rear end arranged to abutthe front end of the annular wall 15 on the part 12. The part 13 iscentered with respect to the part 12 by an annular flange 22 whichextends axially rearwardly from the radial flange 21 and engages theinner surface of the annular wall 15 on the part 12. As shown in Figure2 of the drawings, the in- 2,797,643 Patented July 2, 1957 vice nersurface of the flange 15 is fashioned with a recess 23 for receiving theaxially extending flange 22, and the radial flange 21 is removablyclamped to the wall 15 of the part 12 by fastener elements, such asscrews 24. The arrangement is such that the two casing parts cooperatewith one another to form a chamber 25 which communicates with the recess18 to receive fluid under pressure admitted through the inlet port 16.

Iournalled in the casing part 13 is a drive shaft 26 liav ing anenlargement 27 intermediate the ends thereof. The rear end of the shaft26 abuts the rear wall 14 of the casing part 12 and the front end of theshaft extends through an opening formed in the front wall of the casingpart 13. Suitable ball bearings 28 are supported within the casing part13 in side by side relationship and engage the shaft 26 at the frontside of the enlargement 27 ,on the shaft. A suitable seal 29 is providedin the casing part 13 between the front wall of the latter and theadjacent bearing 28 to prevent the escape of iluid from the chamber 25.

Secured to the rear end of the shaft 26 is a rotor 30 having a pluralityof radially extending circumferentially spaced cylinders 31 forinedtherein. The cylinders 31 open at the radially outer ends thereof intothe chamber 25 and each cylinder has a port 32 at the radially inner endpositioned to successively register with the recess 1S and arcuate slot20 in response to rotation of the rotor 30 by the shaft 26. As shownparticularly in Figure 2 of the drawings, the rear side of the rotor 30has a bearing engagement with the front surface of the rear wall 14 toprovide in effect a seal around the arcuate slot Zl.

Slidably supported in each cylinder 31 is a piston 33 having a ball 34rotatably supported at the outer end thereof in a position to have arolling engagement with the inner surface of a cam ring 35. Theperipheral portion of the ring 35 projects into the annular recess 23and is clamped to the casing part 12 by the axially extending ilange 22on the casing part 11. The balls 34 on the outer ends of the pistons 33are yieldably urged into engagement with the inner surface of the ring35 by coil springs 36 respectively located within the cylinders 31between the radially inner ends of the pistons 33 and the bottom wallsof the cylinders.

As shown in Figure 5 of the drawings, the inner surface of the ring 35is contoured to provide a cam surface 37. The cam surface 37 is shapedto control movement of the pistons 33 in their'respective cylinders 31.More particularly, the cam surface 37 is designed to move the pistons 33radially outwardly as they move past the recess 18 so that fluid flowsfrom the chamber 25 through the ports 32 into the cylinders 31 at theradially inner ends of the pistons 33. When the cylinders thus lilledwith fluid move beyond the recess 18, the ports 32 are closed by thesurface of the rear wall 14 and as the filled cylinders approach thearcuate slot 20, the pistons 33 in the cylinders are moved radiallyinwardly against the action of the springs 36 by the cam surface 37 toforce lluid under pressure through the ports 32 and slot 2t) into theoutlet port 17. The outlet port 17 is connected to the equipmentrequiring lluid under pressure for operation and this equipment is notshown herein.

The embodiment of the invention shown in Figure 6 is identical to theone previously described with the exception that provision is made foradjusting the ring 35 to vary the position of the cam surface 37 andthereby alter the displacement of the pump. As shown in Figure 6 of thedrawings, the cam ring 35 is formed with diametrically opposed llatsurfaces 38 which respectively slidably engage corresponding surfaces onthe part 12 of the casing 11. Sliding movement of the cam 35 in oppositedirections relative to the casing 11 is accomplished by a pair ofpistons 39 and 40 positioned to respectively engage diametricallyopposite sides of the ring 35' midway bctween the flat surfaces 38. Thepistons 39 and 40 are respectively slidably supported in cylinders 41and 42. In practice, the cylinders 41 andv 42 may be formed integralwith the casing part 12.

It will'v also be noted from Figure 6 of the drawings that the cylinders41 and 42 have ports 43 at the outer ends of the pistons and these portsare respectively connected to tubes or conduits 44 and 45.

The conduits 44 and 45 are alternately connected by a valve 46 to thehigh pressure side of the system or, in other words, to the outlet port17 and to an exhaust passage or drain which will be presently described.The valve 46 comprises a casing 47 and a plunger 48 slidably supportedin a bore or chamber 491 extending axially through the casing 47. Thevalve casing 47has axially spaced .ports 50' and 51 intermediatethe endsthereof communicating with thechamber 49 and respectively connected tothe conduits 44 and 45. The front end of the chamber 49 has a port 50which is adapted for connection to the pressure side of the system or,in other words, to the outlet port 17 of the pump. The rear end of thechamber 49 'is closed by a stop 51 slidably mounted in the chamber 49and secured to the front end of a stud 52 which is threadably mounted ina bushing 53 fixed in the rear end of the chamber 49. A spring 54 isinterposed between the stop 51 and the adjacent end of the valve plunger48 tending to move the latter in a forward direction to the positionthereof shown in Figure 6 of the drawings.

The valve plunger48 has axially spaced reduced portions which providethe plunger'. with three enlargements, 55, 56, and 58. Also the valvecasing 47 has two bypasses 59 and 60. The bypass 59 connects the frontend of the chamber 49 to the intermediate portion of the chamber locatedbetween the ports 50 and 51. The bypass 60 connects axially spacedportions of the chamber 49 to a drain or exhaust passage 61.

The above construction is such that vwhen the valve plunger 48 is in itsforwardmost position shown in Figure 6 of the drawings, the enlargement55 closes the front endof the bypass 59 and thereby` prevents the ow offluid underk pressure to either of the-conduits 44 and 45. However,shouldthe force acting on the enlargement '5 exceed the force appliedbythe coilfspring 54, the valve plunger 48 will move rearwardly-.againsttheaction of the spring 54 to a position depending upon the setting ofthe stop 51 or upon the resistance offered by the spring -54 tocontinued movement of the valve plunger 48. In the event the pressureacting on the front end of the valve plunger 48 becomes sufficient tomove the plunger to the position shown in Figure 7 of the drawings,.therear end of the bypass 59 is opened by the enlargement 56 and the drainpassage 61 is opened by the enlargement 58. Hence, fluid under pressureows throughvthe bypass 59 into the conduit 45 and cylinder 42 to shiftthe cam 35 in an upward direction. As a result the displacement of thecylinders 31 in the pump 10 is reduced and the output of the pump iscorrespondingly reduced.

Assuming now that the pressure acting. on the enlagement 55 of thevalveplunger 48 drops below the pressure exerted by the spring 54, itwill be noted that the valve plunger 48 is shifted forwardly. Uponpredetermined forward movement of the plunger 48, the enlargement 58 onthe plunger closes the drain passage 61 and the rear end of the bypass59 is connected to the conduit 44. Also, the bypass 60 is opened by theenlargement 55 so that the drain passage 61 communicates with theconduit 45. As a result, the cam 35' is shifted downwardly relative tothe valve casing 11 and displacement of the cylinders 31 in the pump 10is increased. It follows from the abovethat shifting movement of the cam35 to vary displacement of thev pump pistons depends on. the forceapplied to the plunger 48 by the spring 54 and, hence, the output of thepump may be varied by adjusting the stopl 5-1.` It also follows that fora given spring adjustment thel valve 46 renders it Apossible to assureobtaining substantially uniform pressure at the outlet port 17 of thepump regardless of variations in the speed of rotation of the ptunprotor 30;

What I claim as my invention is:

A pump structure comprising a housing having a chamber provided with anintake port and a discharge port, a rotor supported for rotation in saidchamber and provided with pump spaces which successively communicate inthe rotation of said rotor with said intake and discharge ports, a pumpmember movably supported in each pump space, a cam engaged` by saidmembers in the rotation of said rotor and mounted for adjustmentrelative to the latter tovary'thedisplacement of said-pump members, apair of uid pressure actuated pistons acting oppositely on said camtoAadjust the same, aV valve housing having an axialv chamber and apair ofpassages each communieating with one of said pistons; said Valve housingalso having twoY other passages communicating respectively withsaiddischarge-port and a drainport, a control means comprising aV pistonvalve having three spaced enlargements for closing said passages, andbiasing means for moving said valve to a position Vwhere both of thepas.- sages communicatingV with said pistons are closed by a rst pair ofsaid enlargements, said valve beingv subjected to.v fluid pressure insaid discharge port and opposing said biasing means, said valve whensubjectedl to a predetermined increase of said opposing fluid pressurebeing m'oved to a second position inwhich one of the passagescommunicating with one of said pistons is in communication with saiddischarge port and the other of said passages communicating with theother of said pistons is in communication with said drain port, saidvalve when subjected to a greater predetermined increase of saidopposing fluid pressure being movable to a third position in which saidpiston valve interrupts communication between the fluid pressurecontrolled-pistons and the drain port, said valve when subjected to astill greater pressure bei-ng movable to a fourth position in which saidone passage is in communication with said drain port and said otherpassage is in communication with said discharge port.

References Cited in the file of this patent UNITED STATES PATENTS2,238,061 Kendrick Apr. 15, 1941 2,238,062. Kendrick Apr. 15, 19412,238,063 Kendrick Apr. l5, 1941 2,309,148 Wilson et al. Jan. 26, 19432,406,138 Ferris Aug. 20, 1946 2,453,538 Rauch Nov. 9, 1948 2,470,220Mott May 17, 1949 2,557,508V Leibing June 19, 1951 2,612,110 DelegardSept. 30, 1952 FOREIGN PATENTS i 470,950 France.4 June 29, 1914

